The present invention relates to an extruded or drawn brass material. More particularly, the invention relates to a brass material for forging which exhibits excellent forgeability, dezincification resistance, mechanical properties, and free cutting properties.
A brass material exhibits poor hot forgeability when a specific amount of ductile beta phase is not produced during hot working.
On the other hand, when the beta phase is produced in addition to the alpha phase in the microstructure after forging, dezincification tends to occur at the beta phase.
A brass material containing only the alpha phase may be obtained by adjusting the Cu content to more than 63%. However, such a brass material cannot be applied to hot forging due to high hot resistance.
Moreover, such a brass material shows poor mechanical properties (e.g. tensile strength).
In order to deal with this problem, the beta phase may be caused to disappear by forging a brass material having a Cu content of about 61% and subjecting the forged brass material to a heat treatment.
JP-A-2000-169919 discloses a lead-free brass material having a Cu content of 60.5 to 63.5 wt % and containing Ni and Sn in order to provide the brass material with dezincification resistance, strength, and the like.
However, since this technology suffers from insufficient forgeability, the brass material must be subjected to a heat treatment or annealing in order to ensure corrosion resistance.
JP-A-2003-247035 discloses a Cu—Zn—Sn—Si-based brass material exhibiting dezincification resistance. However, this brass material exhibits insufficient hot forgeability.